The following publications are believed to represent the current state of the art:    Microbial Fuel Cells: Methodology and Technology, Bruce E. Logan et al, Environ. Sci. Technol., 40 (17), 5181-5192, 2006;    Microbial Fuel Cells—Challenges and Applications, Bruce E. Logan & John M. Regan, Environ. Sci. Tech., 40 (17), 5172-5180, 2006;    Stefano Freguia, Korneel Rabaey, Zhiguo Yuan, Jurg Keller, Non-catalyzed cathodic oxygen reduction at graphite granules in microbial fuel cells, Electrochimica Acta, 53, 598-603, 2007;    Hong Liu et al., Quantification of the internal resistance distribution of microbial fuel cells, Environ. Sci. Technol., 42 (21), 8101-8107, 2008;    US published patent application no. 20070259217; and    PCT published patent application no. WO 2010/049936.